1. Field of the Invention
The present invention relates to the use of an x-ray system for cancer treatment. More specifically, the present invention relates to the use of an x-ray system with an implantable needle for treating tumors.
2. Background Art
There currently exist x-ray systems which include lower power x-ray devices (x-ray tubes) which are implantable into a patient""s body for directly irradiating a desired region of tissue with the x-ray. The ability to deliver x-ray radiation to the tumor is the main advantage this system. For tumor treatment, Compton scattering and photoionization are the most important effects of interactions of x-ray radiation with biological samples. For the dominant photoelectric effect the probability of atom ionization decreases with increasing photon energy as an inverse third-power law. In other words, an x-ray beam with the energy of 10 keV delivered directly to the tumor will be 125 times more effective when absorbed compared with a 50 keV x-ray beam. But low energy radiation provides very limited penetration of tissue, and is thus useful only in treating skin lesions.
The known x-ray device miniaturized low power x-ray source U.S. Pat. No. 5,153,900, Oct. 6, 1992) which is implantable into a patient body for direct delivery of x-ray radiation has the following disadvantages:
1. The tube has very limited power, because the x-ray source should be small enough to be implanted into the body. For treatment of tumors, for example brain tumors, a high dose rate for single dose irradiation is generally preferred, therefore this tube does not provide sufficient radiation as required for treatment.
2. High vacuum x-ray sources with high voltage (up to 90 kV) are difficult to implant into a human body.
3. Besides including predefined xe2x80x9cusefulxe2x80x9d x-ray energy, the spectrum of the x-ray beam also includes an x-ray energy continuum, known as bremsstrahlung, which can destroy healthy tissue.
4. During relatively long exposures (several minutes) the temperature of anode which is set on the end of implantable x-ray source may rise sufficiently.
5. The x-ray device should be used in environments in which there are low level dc and ac magnetic fields which are capable of deflecting the electron beam from the anode of implantable x-ray source. Special measures therefore need to be taken against the influence of outside electric fields on an electron beam.
6. There is a large (from 5 to 7 mm) diameter for the implantable x-ray source.
It would therefore be useful to develop an x-ray device which can overcome the obstacles set forth above.
According to the present invention, there is provided a method and apparatus for the treatment of cancer by delivering x-ray radiation directly to a desired region of tissue, including tumors. An object of the present invention is to allow adjustment in energy, flux intensity, and shape of the x-rays delivered to the tissue, utilizing an x-ray tube or a linear accelerator with a thin anode, any known type of conditioning optics (multilayer optics, crystal, capillar optics, aperture, and etc.) which direct x-ray radiation and implantable needles with the means for shaping x-ray radiation. Another object of the present invention is to increase x-ray flux directed to the needle through the use of a linear accelerator with a thin anode. This modified accelerator has a narrow sharp space distribution of emitted x-ray radiation even for a low energy (50 kV and less) x-ray beam. For optics with a small (less than 1 degree) angular aperture, this x-ray source allows a more than three orders of magnitude increase in flux directed to the needle.